Light therapy systems have been widely used for some time to treat circadian rhythm disorders, seasonal affective disorder and other such problems by delivering light through the eyes of a subject. One problem has been the need to provide the necessary light intensity and color spectrum, similar to daylight. In many cases fluorescent lights are used because they tend to provide an effective spectrum of light and are longer lasting than incandescent lamps. However, the high intensities of light needed for such treatments required relatively large-sized lamps and other components. Thus, many commercial light therapy units have been large, bulky and cumbersome.
In the last decade, advances in ballast and fluorescent light technology have allowed some companies to produce smaller, lighter-weight light therapy units. An example is shown in U.S. Pat. No. 6,488,698 (Hyman). Such units, though smaller and less cumbersome than previously mentioned designs, are usually too large to be hand-held. Further, the Hyman device has no display or other means to convey information.
Some products have been made portable by developing wearable devices which bring the light source close enough to the subject's eyes to achieve the effective high-intensity lux output. These units typically incorporate smaller, less intense lamps that can be battery powered. Examples are shown in U.S. Pat. No. 5,447,528 (Geraldo); U.S. Pat. No. 6,350,275 (Vreman et al.); and U.S. Pat. No. 6,053,936 (Koyama et al.).
Such devices tend to flood the user's field of vision with light. This makes it difficult for the user to look past the bright light source to more dimly lit surfaces to accomplish daily tasks. This arrangement can cause eyestrain, headache and other discomforts.
Another approach involves using LEDs to try to make portable devices. However, prior art LED ocular devices tend to be harsh to the eyes and create retinal after imaging. Prior art LED devices are of limited portability because of power consumption that requires access to an external power outlet or relatively large cumbersome batteries, rather than using a portable or built-in battery pack.
Some products have addressed the portability and eyestrain problems by developing devices worn against the skin. These non-ocular approaches radiate light energy through the skin to the blood stream. Examples are shown in U.S. Pat. No. 6,135,117 (Campbell et al.) and U.S. Pat. No. 6,350,275 (Vreman et al.). These units have not yet been proven effective in large clinical trials.